Extreme heat grounds commercial planes in Phoenix

George Mason University’s Jim Kinter says the science is pretty straightforward concerning this week’s decision by several airlines to cancel flights because of excessive heat in the Southwest.

“The hotter and more humid the air, the less dense it is,” said Kinter, director of George Mason’s Center for Ocean-Land-Atmosphere Studies and a professor of climate dynamics, in an email. “For airplane flight, it is essential that airplane wings obtain lift, which is the force exerted by the air to the underside of the wing.”

Less air density means planes achieve less lift and climb slower, thereby requiring additional distance for both takeoffs and landings, Kinter said.

The issue has rarely been a problem, but the Southwest, at the time, was enduring its worst heat wave in decades, prompting several airlines to cancel flights out of Phoenix’s Sky Harbor International Airport.

Temperatures had reached 118 degrees in Phoenix on June 19 before climbing to 119 on June 20, the city’s fourth-hottest day ever.

That temperature threshold for smaller planes is lower, but it’s rare to see bigger aircraft sidelined. In this case, regional flights were most adversely affected by the soaring temperatures, while the larger Airbus and Boeing aircraft engineered for a wider range of operating temperatures were still able to safely fly.

The problem could be an extended one as reports by the U.S. National Weather Service indicate better-than-average chances for higher temperatures than normal for Arizona and Utah from July to September.

“That all weighs in favor of seeing more such temporary groundings later this summer,” Kinter said.

Kinter warned of rising global temperatures making similar scenarios more likely in the future. Mason professor of systems engineering and operations research, John Shortle, agreed.

“I expect the frequency of such heat-related events to increase over time,” he said. “But the extreme heat is not the only source of delay. Connective weather is a big contributor. To me, a larger question is the extent to which climate change will increase the frequency of these other types of events, like severe thunderstorms, which are larger contributors to delays.”

Jim Kinter can be reached at ikinter@gmu.edu or 703-993-5700.

John Shortle can be reached at jshortle@gmu.edu or 703-993-3571.

For more information, contact John Hollis at 703-993-8781 or jhollis2@gmu.edu.

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